Dynamic mechanical properties of solution-cast poly(l-lactide) films

Dynamic mechanical measurements were conducted on different kinds of poly(l-lactide) (PLLA) films to understand the transformation of internal structure of PLLA by both processing and annealing. Effects of annealing condition on the properties of PLLA films including crystallinity change were investigated by wide angle X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results from this study indicate that PLLA films made by both casting and pressing processes exhibit significantly different dynamic mechanical behavior and that the solvent casting process is relatively suitable for retention of mechanical properties because of the development of the crystalline phase even below the glass-transition temperature, Tg. Moreover, the results of the dynamic mechanical analysis reveal a simpler relationship between the thermal history and the internal structure of the PLLA films prepared by solution casting, compared with that of PLLA films prepared by pressing.